Growing Crystals from Solutions

LAB 14: Growing Crystals from Solutions. bobby. In this lab the effects of temperature on crystal growth is examined. It is hypothesized that lower temperature was yield higher amounts of crystals and larger crystals. The technique used to test the hypothesis is the evaporation of solutions, prepared by dissolving a compound in water at near boiling temperatures. These solutions were then split into three different test tubes that contain a piece of copper, which will acted as a surface in which nucleation, the process that begins the formation of crystals, may occur. These test tubes were placed in three different temperature zones. One was in the refrigerator which is set at around 3-6 degrees Celsius, another in oven set at 36 to 40 degrees Celsius, and finally the last test tube was placed out in room temperature which is around 22-25 degrees Celsius in the chemistry room. After the solutions were allowed to sit for at least 2 days in their designated locations, it was observed that only one of the twelve test tubes contained no crystals. All of the rest of the tubes contained a crystal either in the solution or at least on the walls of the test tube. Other than the results of the sodium thiosulfate solution, which most likely did not have enough of the compound dissolved in the solution, all of the results showed that the hypothesis was only partially supported through this experiment. Our observations showed that the coldest environment, the refrigerator, created the highest amount of crystals; however it did not produce the largest amount of crystals. The largest crystals were formed in warmer temperature environments. This means that nucleation may occur more frequently in lower temperatures, but gradual cooling of solutions in higher temperature environments may form larger crystals.
Key Words: Crystallization, nucleation, solutions, temperature, dissolved, size, amounts

Compound	Refrigerator Results (3-6 degrees Celsius)	Room Temperature Results (22-25 degrees Celsius)	Oven Results (36-40 degrees Celsius)
Sodium thiosulfate	· No crystals in solution · Flat clear colorless crystals · above the surface of the solution on the test tube walls · small crystals	· No crystals in solution · Flat clear colorless crystals · Above the surface of the solution on the test tube walls · Smaller crystals than the refrigerator results	· No results
Epsom salt	· White moist solid · Densely packed very fine crystals · No liquid visible	· White very moist solid · Less densely packed than refrigerator sample · Very fine crystals · No liquid visible · Slightly larger than the fridge results	· Large white semi-transparent crystals · Larger crystals on top · The results are very solid and hard · Lots of small crystals going up the sides of the test tube
Washing Soda	· Similar to Epsom Salt results but crystals are larger · The clusters of crystals are easily broken apart · Moist, white · No visible liquid	· Very large semi-transparent crystals · Take up about three quarters of the solution · Some small crystals exist above the solution on the sides of the test tube	· No crystals in solution · Very small crystals on the walls of the test tube · Clear colorless crystals
Potassium ferrocyanide	· Many small yellow crystals · Some liquid still left over · Lots of crystals · Take up around half of the solution · Easily broken apart	· Slightly larger yellow crystals · Easily broken apart, yet a little more difficult than the refrigerator results · About the same ratio of crystals to liquid	· Larger crystals than room temperature results · Dark orange copper color · Harder than the fridge and room temperature results to break apart group of crystals · About the same ratio of crystals to liquid, with perhaps a little less liquid

Washing Soda, Epsom Salt, and Sodium Thiosulfate Crystals (From left Room Temperature Results Oven Results Refrigerator Results)



Potassium Ferrocyanide Crystals (from left Refrigerator, Room Temperature, Oven)

Journal Article: Spatial Control of Crystal Nucleation in Agarose Gel.

Researchers have discovered a method by which they are able to cause crystallization to occur in minutes as opposed to days. The usage of a low-intensity laser causes nucleation to happen accurately in a desired location. A team led by Andrew J. Alexander used the technique observed by Bruce Garetz, Allan Myerson, and fellow researchers at the Polytechnic Institute of New York University. Based on the findings that lasers could cause supersaturated urea solutions to crystallize, Alexander and his team prepared an agarose gel with supersaturated potassium chloride. They covered the gel with a mask and exposed it with 6-nanosecond polarized pulses from unfocused YAG lasers. This approach called nonphotochemical laser induced nucleation caused crystals to form immediately in the areas the lasers hit. Although the method has worked with the gel, it has not been perfected with proteins and there are still many questions to be answered about the laser-induced nucleation process. This discovery may be used in the future to control the structure of semiconductor materials or aid scientists working on diffraction experiments.
Rowe, Aaron A. 2009 August 10. Lasers Spark Crystal Growth. Available from: http://pubs.acs.org/cen/news/87/i32/8732notw7.html (Accessed 2010 January 21).
Duffus C., Camp P.J., Alexander A.J. 2009 June 25. Spatial Control of Crystal Nucleation in Agarose Gel. Journal of the American Chemical Society. 131(33):11676-11677